I hope I thought of everything Pete, but please feel free to ask questions, or if you have any input I sure would like to hear it. Right now would be the time to make a change to the design.

The design evolved over a long time. I have been working on it on and off for over two years. So there were a lot of design decision that had to be made. It's also my first IC engine I designed myself and I'm curious to see if everything is going to work out the way I imagined while drawing it up.

360degree crank should be OK The Nemett Bobcat which is a similar layout model engine runs OK with one, the designer did an article or two about crank layout Vs vibration and decided the 360 was the best for his engine.

Hi Yogi,I'm guessing that the cover plate on the head is so you can create water passages in the head and then seal it off? If this is correct then you might have some issues with the valve guide alignment as they go from the head to the cover plate. I might suggest putting a couple of registration dowels in the head and cover plate so that the two pieces stay in exact alignment when machining and assembling. gbritnell

George, thank you for your input. You are correct. The top plate is so I can seal off a cooling passage machined into the head. I came up with the following solution to the problem you pointed with the valve guides alignment: The holes for the valve guides in the cover plate will be machined over size, to allow for the machining tolerance. Also, the valve guides will be stepped down to a smaller diameter at the top. This would prevent the valve guide from working its way out of the cylinder head from the combustion pressure. Even though to common practice of pressing them into the head has proven to be more than adequate, I felt this would be worth while.

Roger, the exhaust passage is actually a straight hole, but it's at an angle to clear all the mounting holes. The section cut was done parallel to the plane, that's why it looks tapered. To better illustrate, I attached a couple of renderings.

I like your twin cylinder design. It reminds me of the Bob Shores Silver Bullet I built. I think you'll find you can easily start your engine with a hand crank. Definitely add the over running bearing as George mentioned.